mast [ mast, mahst ] noun: nuts, seeds, or other fruits of some woody plants, including trees, shrubs, and vines, that serve as food for wildlife, especially when accumulated on the forest floor
The word mast comes from the Old English maest, meaning “fodder,” and is believed to be derived from a prehistoric German word meaning meat. The word was originally applied in agriculture to food provided by nature for domestic animals (particularly hogs but also cattle, sheep, goats, and even chickens) that foraged in the woods near homes and farms. The link to a word for meat makes sense, as nuts are foods rich in fat, carbohydrate, and protein, providing a lot of energy for their size.
In horticulture today, mast is divided into “hard mast” (nuts such as acorns, beechnuts, hickory nuts, walnuts, hazelnuts, and pecans, as well as seeds with hard exteriors) and “soft mast” (fleshy fruits such as persimmons, apples, serviceberries, blueberries, and holly drupes, as well as fungi and the buds of trees). The latter are more perishable, often lasting only days, as is the case with the tasty and beloved serviceberry fruits, harvested by birds directly from the tree’s branches. Some soft mast crops are critical food sources for both local and migrating birds and other creatures.
Hard Mast Trees
Nuts, high in crude fat and crude protein, are essential fall and winter food sources for wildlife. Left to right: Carya ovata, Corylus avellana ‘Contorta,’ Fagus grandifolia, Juglans nigra, Quercus acutissima, Quercus phellos.
Soft Mast Woody Plants
Berries, pomes, and drupes, all high in carbohydrates, provide nourishment for wildlife from early summer to fall and sometimes beyond. Left to right: (1st row) Phytolacca americana (August berries), Diospyros virginiana (October berries), Parthenocissus quinquefolia (October berries), Amelanchier arborea (May pomes), Aronia melanocarpa (July pomes), Crataegus crus-galli (October pomes); (2nd row) Rubus fruticosus ‘Chester’ (July etaerio of drupes), Prunus serotina (July drupes), Cornus florida (August drupes), Nyssa sylvatica (August drupes), Ilex opaca (October drupes), Ilex verticillata ‘Red Sprite’ (February drupes).
Some mast crops appear yearly, others can take two years or more to mature. Good mast years with bumper crops (above annual median production) of nuts or fruits appear less regularly, with the cycles influenced by weather, insects or disease, and tree age (aging forests may bear less and are often not regenerated due to habitat loss, climate change, and disease). A bumper crop of mast depends also to a considerable extent on synchronicity, the simultaneous occurrence of the boom in nuts or other fruits in a fairly wide area. Scientists have discovered that often when there is a big mast year on the East Coast of the United States, the western states will have a bust year —and vice versa. A bumper crop is frequently followed by several years of lower production. The “boom” crop usually fosters higher birth rates among the creatures who dine on mast, but then in the following “bust” year they may need more than is produced, leading to starvation and reduction in numbers—a true boom and bust cycle that goes beyond the mast crop. The white-footed mouse, for example, feeds on mast; it is also a reservoir for the ticks that carry Lyme disease, so a boom mast year increasing this population of tiny rodents can increase the prevalence of ticks and the disease.
In Virginia, the chief hard mast crops are acorns and beechnuts. The edible parts of nuts, the nutmeats, have more calories in proportion to their size than many forms of animal protein, including beef and pork. Nuts also have an extended “shelf-life,” meaning they will in many cases last through the winter season, when food is otherwise scarce, providing sustenance for many species, including squirrels, blue jays, and crows, mice and voles, woodpeckers, titmice, wild boars, wild turkeys, ducks, black bears, white-tailed deer, opossums, and raccoons. Some of the foragers of acorns and other mast also serve as dispersal units, carrying the seeds farther from the originating trees or shrubs than simply under the parent plant.
Because of their high tannin content, acorns are toxic in large quantities to many animals, including humans (but not hogs). Indigenous Americans knew this and soaked acorns before using them as food. In times of scarcity, early settlers learned to make substitute “coffee” from leached acorns as well. Excess bitterness of red oak acorns has been thought to make them less desirable to squirrels than those of white oaks. Some have speculated that when all the white oak acorns are eaten, and the autumn rains and later snows and thaws have leached much of the tannin out of the buried acorns, the squirrels do get around to the red oak acorns. However, a few scientists have discovered that tannin levels of buried acorns do not diminish with time (Smallwood et al. 2001). They posit that in fact the red oak acorns are more widely buried and consumed than the white ones because they do not germinate until spring and are less perishable, while the white oaks germinate in fall. The germinating embryo uses nutrients to put out downward root growth before the first frost, but the first leaves of the cotyledon do not appear until the following spring. White oak acorns that squirrels did bury were usually missing the embryo, which the squirrels had excised beforehand. Red oak acorns were buried intact unless the squirrels sensed they were germinating in which case the embryos were sometimes removed. Researchers also observed that squirrels ate only the top halves of red acorns and cast away or often buried the bottoms where the tannin is most concentrated. This practice may leave the embryo, also located at the bottom of the acorn, undamaged and able to germinate. In any case, it seems clear that the distribution of hard mast crops like nuts is a major factor in forest regeneration of these tree species.
White Oak and A Red (Willow) Oak
Many wildlife prefer the hard mast of Quercus alba (white oak), but its production is highly variable year to year, while Quercus phellos (willow oak) produces a good seed crop most years providing an important and fairly reliable food supply for game and other animals.
Left to right: Quercus alba (stages of acorn development, young and mature trees).
Left to right: Quercus phellos (stages of acorn development, mature tree, mast, cupules and nut).
Red and white oak acorns are among the mast crops tracked in Virginia and according to the 2022 report from the Department of Wildlife Resources, the red oak acorn crop was below the long term survey median of 19.7% for the second year in a row. It estimated only 8.4% of individual tree crowns were covered with acorns. This lower crop level was reported in all but one of the 17 mountain sites surveyed, and in all the Piedmont and most of the Tidewater sites reporting. White oaks, on the other hand, bore fruit above the median rate of 10.8% for the first time in four years. In the mountains, the crop was just above average; in the Piedmont it was higher, with a range of 30–32% of crowns bearing acorns; Tidewater’s three sites came in lower, but still better than in the previous year, and numbers there are regarded as uncertain due to low sample size. The last very good mast years for eastern oaks were in 2010 and 2012 when the estimated crown cover in Virginia was respectively 60.6% and 57.2% for white oaks and 77.9% and 65.2% for red oaks. Because acorn production is vital to forest regeneration, but so variable from year to year and region to region, the Virginia Department of Forestry requests help from Virginia residents annually in September and October in gathering the acorns of certain native species, from which it can grow seedlings to transplant throughout the state.
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References
Binion D, Stein JD, Acciavatti RE. 2003. Field Guide to Native Oak Species of Eastern North America. United States: U.S. Forest Service, Forest Health Technology Enterprise Team.
Burns RM, Honkala BH. 1990. Volume 2. Hardwoods. Silvics of North America. Forest Service. USDA.
Griep MT. 2001. Hard and Soft Mast. Southern Forest Resource Assessment. USDA Forest Service Southern Research Station and Southern Region. (accessed October 31, 2022).
Martin K. 2022. 2022 Acorn Production Report: Mixed Results. Virginia Department of Wildlife Resources.
McCay S. November 2017. Wild Pigs and Mast Crops. Texas A&M Natural Resources Institute Journal.
Pearse IS, Koenig WD, Kelly D. August 2016. Mechanisms of mast seeding: resources, weather, cues, and selection. New Phytologist. 212(3): 546–562. doi: 10.1111/nph.14114.
Sekerak CM, Tanner GW. March 1994. Reviewed June 2020. Making the Most of Your Mast. SS-FOR-3, 1994. University of Florida/IFAS extension.
Smallwood PD, Steele MA, Faeth SH. August 2001. The Ultimate Basis of the Caching Preferences of Rodents, and the Oak-Dispersal Syndrome: Tannins, Insects, and Seed Germination. American Zoologist. 41(4): 840–851. doi: 10.1093/icb/41.4.840.
Tallamy DW. 2021. The Nature of Oaks. pp. 14-26. Timber Press, Portland, OR.
University Of Richmond. November 1998. Researchers Tackle The Nutty Truth On Acorns And Squirrels. ScienceDaily. (accessed November 13, 2022).